diff --git a/dac_data.py b/dac_data.py
index 37f7018..64410ce 100644
--- a/dac_data.py
+++ b/dac_data.py
@@ -35,7 +35,7 @@ def __init__(self, pins, swap=((0, 3), (1, 8))):
         self.comb += [
             Cat(words).eq(Cat(self.data)),
             par.eq(Cat([parity(*word) for word in self.data])),
-            self.istr.eq(i[-1]),
+            self.istr.eq(i[0]),
         ]
         self.sync += [
             i.eq(Cat(i[-1], i)),